The overall objective of the research program is to develop an implantable passive artificial muscle system which will function similarly to the natural muscle being replaced. The artificial muscles are currently fabricated of silicone rubber or polyurethane and twenty-two surgical prodedures have been conducted on sheep to date. Some of the artificial muscle systems have had either a strain gage or load-cell incorporated so that the in vivo muscle dynamics could be followed with time. The longest implant to date has been ten months with the majority of muscles installed under the following pre-load conditions: dorsal flexion (2.0 to 8.5 lbs) and plantar flexion (6.0 to 12.2 lbs). The results of the in vivo studies indicate the natural tendon - artificial tendon attachment scheme is probably unsatisfactory since necrosis of the tendon (both proximal and distal attachment points) has occurred in a large percentage of the procedures. A more satisfactory approach for installation of the artificial muscle system appears to be a titanium alloy bone-pin and Mersilene suture attachment scheme using both the silicone rubber and polyurethane artificial muscle systems. BIBLIOGRAPHIC REFERENCE: Mills, E.J., Gardner, D.L., Hughes, K.E., and Pinson, R.C., "Load Measurements on Artificial Muscle Systems", Proc. 29th Annual Conf. on Eng. in Medicine and Biology, p 247 (Nov. 1976).